1. Technical Field
The present invention relates generally to water pumps, and more particularly to a secondary seal for a centrifugal pump.
2. Background Art
Next to electric motors, mechanical pumps are the most common machine in the world, and centrifugal pumps are perhaps the most widely employed type of pump inasmuch as they are well suited to pumping high volumes of water with a smooth flow. However, centrifugal pumps are notoriously prone to leaks due to mechanical seal failures in the seal chamber between the pump housing and the motor casing. Damage from leaks is not limited to the environment surrounding the pump; often damage extends to the pump itself, most notably including the motor flange, which can suffer rapid corrosion, particularly when a primary mechanical seal failure exposes the motor flange to salt water or chemicals used in the treatment of pool and spa water. Accordingly, it is desirable to have a means to drain fluid that might collect in the pump seal chamber and divert it from contact with the pump motor flange.
Several pump back-up seals have been devised. A few exemplary patents disclosing such solutions include: U.S. Pat. No. 4,375,291, to Padgett, which teaches a pump assembly having primary and back-up or secondary seals, the latter provided to prevent the escape of fluid being pumped from the pump housing upon failure of the primary seal assembly. The secondary seal includes a ring supported against rotation and surrounding the drive shaft or the shaft sleeve. The ring support is constructed of a material which will collapse under pressure of the pumped fluid if the primary seal fails, thereby sealing the space between the shaft and the housing or case to prevent fluid from escaping to the exterior of the housing.
U.S. Pat. No. 6,287,074, to Chancellor, shows a centrifugal pump having a bearing assembly with a rotating portion that rotates with the motor shaft, and a non-rotating portion that doesn't rotate with the shaft. The bearing assembly is disposed outside the fluid flow path. A non-rotating seal is axially slidable on the motor shaft, and a surface of the slidable seal is biased against a surface of the rotating portion of the bearing assembly to form a primary seal. A non-rotating secondary seal seals the non-rotating sealing member and is not in direct contact with the bearing assembly.
U.S. Pat. No. 5,540,449, to Algers et al., teaches a back-up pump seal for use with a centrifugal pump having a rotating shaft, and the seal assembly includes a movable primary seal rotatable with the shaft and a fixed secondary seal axially spaced along the shaft from the primary seal. It further includes an inlet for flushing liquid, an outlet for the flushing liquid and for pump medium that leaks through the primary seal, a collection chamber between the primary and secondary seals for flushing liquid and leaking pump medium, and a drain passage connecting the collection chamber and outlet. The collection chamber is divided into at least two portions in liquid communication with each other and with the drain passage to assure that the flushing liquid is maintained between the primary and secondary seals for an extended period of time for advantageously efficient use of the flushing liquid in lubrication and cooling of the primary seal.
U.S. Pat. No. 5,660,521, to Serio, shows an alternative solution to leakage due to pump primary seal failure. This patent discloses a water pump adapted for use in an internal combustion engine. The pump includes a leakage drain cavity disposed about the pump motor shaft in the pump housing and including a weep hole extending from the drain cavity outside the housing. A water pump seal is positioned between the pump impeller and the drain cavity and includes a central opening defining a leak path to the drain cavity. A coolant wick of absorbent material is disposed in the drain cavity forming an absorbent barrier in the leak path.
The foregoing patents reflect the current state of the art of which the present inventor is aware. Reference to, and discussion of, these patents is intended to aid in discharging Applicant's acknowledged duty of candor in disclosing information that may be relevant to the examination of claims to the present invention. However, it is respectfully submitted that none of the above-indicated patents disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described and claimed herein.